1. Field of the Invention
The present invention relates to floating magnetic head device installed in, for example, a hard disk drive, and, more particularly, to a magnetic head device and producing method thereof, in which a loading projection (pivot) can be easily and very precisely formed on a supporting member which supports a head body in order to allow the head body to assume a stable floating posture.
2. Description of the Related Art
FIG. 8 is a partial plan view of a conventional magnetic head device for use in a hard disk drive, whereas FIG. 9 is a partial side view thereof.
The magnetic head device comprises a head body 1 and a supporting member 2 which supports the head body 1.
The head body 1 includes a slider 3 opposing a disk D, such as a hard disk, with a thin film magnetic element 4 being provided at a trailing side Y end surface of the slider 3. The slider 3 is made of a ceramic material or the like. The thin film magnetic element 4 includes a MR head (or read head) and an inductive head (or a write head). The MR head detects any magnetic field leakage from a recording medium, such as a hard disk, by making use of the magneto-resistive effect, in order to read a magnetic signal. The inductive head includes, for example, a coil formed into a pattern.
The supporting member 2 comprises a load beam 5 and a flexure 6.
The load beam 5 is composed of a plate spring, and has bent portions 5a, formed into a rigid structure, on both sides of the load beam 5 so as to extend from the front portion to the middle portion thereof. The stem end of the load beam 5 is capable of providing a predetermined resilient pressing force. A spherical pivot 7 is formed near one end of a flat portion 5b formed between the bent portions 5a so as to project downward, in the figure. The head body 1 contacts the pivot 7 through a flexure 6 described below. A positioning hole 8 for alignment with the flexure 6 is formed in the flat portion 5b of the load beam 5.
The flexure 6, composed of a thin plate spring, comprises a fixing portion 6a, a cantilever 6b, and a connecting portion 6c. As shown in FIG. 8, a positioning hole 9 is formed in the fixing portion 6a. After alignment of the positioning hole 9 with the positioning hole 8 formed in the load beam 5, the fixing portion 6a is affixed to the bottom surface of the load beam 5 by, for example, spot welding. A slot is formed in one end of the flexure 6, and the portion separated by the slot forms the cantilever 6b and the connecting portion 6c. Stepped portions 6d are formed in the connecting portion 6c, so that the cantilever 6b is located below the fixing portion 6a.
The top surface of the cantilever 6b abuts against a pivot 7 of the load beam 5. The resiliency of the cantilever 6b allows the head body 1 bonded to the bottom surface of the cantilever 6b to change its posture freely on the bottommost point of the pivot 7 as a fulcrum.
The head body 1 of the magnetic head device is biased towards the disk D as a result of the resilient force provided at the stem end of the load beam 5. The magnetic head device is used in, for example, the so-called contact-start-stop (CSS) hard disk drive. When the disk D is stationary, the bottom surface of the head body 1, due to the aforementioned resilient force, contacts the recording surface of the disk D. When the disk D starts moving, air currents, flowing between the head body 1 and the disk D in the direction of movement of the disk D, produces a floating force exerted on the bottom surface of the head body 1, causing the head body 1 to float a short distance .delta.3 from the disk D.
As shown in FIG. 9, in the floating posture, the leading side X of the head body 1 is lifted higher from the disk D than the trailing side Y. While the head body 1 is assuming such a floating posture, either the MR head of the thin film magnetic element 4 detects a magnetic signal from the disk, or the inductive head writes the magnetic signal information.
The pivot 7 of the load beam 5 is formed by, for example, a pressing machine, such as that shown in FIG. 10, consisting of a punch 10 and a dice 11. The bottom portion of the punch 10 has a spherical face that curves outward. The portion of the top surface of the dice 11 opposing the punch 10 has a spherical hollow. The load beam 5 is placed on the dice 11, and the punch 10 is moved downward, in FIG. 10, to press a portion of the load beam 5 into the spherical hollow in the dice 11, thereby forming the spherical pivot 7 on the load beam 5.
Another method of forming a pivot 7 is illustrated in FIG. 11A. The punch of FIG. 11A has the same form as the punch 10 of FIG. 10, but the portion of the dice 11 of FIG. 11A opposing the punch 10 has a cylindrical hole 11a, instead of a hollow, so that the forms of the dices of FIGS. 10 and 11 are different. Similar to the method illustrated in FIG. 10, in the method illustrated in FIG. 11A, load beam 5 is placed on the dice 11 to press a portion of the load beam 5 downward by the punch 10, thereby forming a pivot 7 on the load beam 5.
However, when pressing machines, such as those shown in FIGS. 10A and 11A, are used, a bottommost point A of the bottom portion of the punch 10 and a bottommost point B of the spherical hollow in the dice 11 (or a line L drawn through the center of the hole 11a in FIG. 11A) may not be on (or lie along) a same vertical line M, causing the bottommost point A and the bottommost point B to be out of line by an amount equal to width T1 in FIG. 11, as well as the vertical line M passing through the bottommost point A and the centerline L to be separated by an amount equal to width T2 in FIG. 12. When pivot 7 is formed on the load beam 5 using a pressing machine, in which the bottommost point A and the bottommost point B are out of line, or the vertical line M passing through the bottommost point A and the centerline L are separated, a bottommost point C on the inner spherically shaped portion of the pivot 7 and the bottommost point B on the outer spherically shaped portion of the pivot 7 are out of line by the amount equal to width T1 in the pressing machine of FIG. 10 and by the amount equal to width T2 in the pressing machine of FIG. 11. This causes the pivots 7 to have ununiform film thicknesses, when they are formed using either one of the pressing machines of FIGS. 10 and 11.
Thus, it is necessary to make widths T1 and T2 as small as possible. In conventional pressing machines, however, tolerances of about 50 .mu.m for the width T1, between the bottommost point A of the punch 10 and the bottommost point B of the dice 11, and width T2, between the vertical line M passing through the bottommost point A and the centerline L of the hole 11a in FIG. 11A, cannot be avoided.
In the pressing machine of FIG. 10, there may also be tolerances due to variations in die processing precision, so that the bottommost point B of the dice 11 is positioned about 5 to 10 .mu.m away from where the dice 11 should actually be positioned. Therefore, in the pressing machine of FIG. 10, the maximum width T1 between the outer bottommost point B and the inner bottommost point C of the pivot 7 as a result of the tolerance becomes as large as about 60 .mu.m.
Crystal grains, such as those shown in FIG. 11B, protrude from the outer side of the pivot 7 formed by the pressing machine of FIG. 11A, causing hills and valleys to be formed near the bottommost point B of the pivot 7. These protruding crystal grains cause the outer bottommost point B of the pivot 7 to be out of line by a even greater amount in correspondence with width T3 (equal to about 10 to 30 .mu.m), so that the maximum width T2 between the outer bottommost point B of the pivot 7 and the inner bottommost point C of the pivot 7 becomes as large as 80 .mu.m.
When the outer bottommost point B and the inner bottommost point C of the pivot 7 are not in line, the following problems arise.
When the head body 1 is floating, the fulcrum on which the head body 1 rocks freely is located at the outer bottommost point B of the pivot 7. Therefore, when the head body 1 is being affixed to the bottom surface of the cantilever 6b of the flexure 6 during assemblage of the magnetic head device, the head body 1 must be positioned so that the bottommost point B of the pivot 7 contacts a predetermined location (about the center) of the upper surface of the head body 1.
However, when the head body 1 is being positioned, the outer edge of the head body 1 is positioned with reference to the bottommost point C of the recess in the pivot 7, ordinarily by using a video camera or the like from the upper surface side of the load beam 5 (see FIG. 8). Then, the head body 1 is bonded to the bottom surface of the cantilever 6b. In other words, while one looks down on the load beam 5 from directly above it, on the assumption that the outer bottommost point B of the pivot 7 is located on the vertical line on which the inner bottommost point C of the pivot 7 is located, the inner bottommost point C of the pivot 7 and the predetermined location of the head body 1 are brought in line using a jig (see FIG. 8).
Thus, as shown in FIG. 12, when the outer bottommost point B of the pivot 7 and the inner bottommost point C of the pivot 7 do not lie on the same vertical line M, so that the bottommost point C of the pivot 7 and the predetermined location of the head body 1 are not in line, a predetermined location E of the top surface of the head body 1 which should contact the outer bottommost point B of the pivot 7 is not in line with the outer bottommost point B of the pivot 7. Therefore, the floating posture of the head body 1, particularly in the rolling direction, becomes unstable.
The larger the separation between the predetermined location E of the top surface of the head body 1 and the outer bottommost point B of the pivot 7, the larger the variation, .delta.4, in the floating amount of the head body 12 in the rolling direction, as illustrated in FIG. 12. The variation .delta.4 in the floating amount of the head body 1 supported by the pivot 7 formed by the pressing machine of FIG. 10 becomes as large as about 20 nm, whereas the variation .delta.4 in the floating amount of the head body 1 supported by the pivot 7 formed by the pressing machine of FIG. 11A becomes as large as about 25 nm. Even if there is a desire to make the head body 1 smaller, and the spacing 63 (shown in FIG. 9) is made smaller, a large variation .delta.4 in the floating amount causes the spacing .delta.3 to be essentially large, thereby preventing high-density recording.
A thin film electrode terminal portion (connecting portion), led out from the thin film magnetic element 4, is formed at the trailing side (Y) end surface of the head body 1. Conventionally, a thin wire was electrically connected to the electrode terminal portion, and extended to the stem end of the load beam, in order to wire the head body 1. Recently, however, another wiring structure was proposed. In the proposed structure, instead of using the aforementioned wire, a thin film signal conducting pattern is formed at the bottom surface of the flexure 6 in order to electrically connect a connecting portion of the signal conducting pattern and the electrode terminal portion of the head body 1.
This wiring structure, however, gives rise to another problem not mentioned above.
In other words, when the head body 1 is aligned with reference to the inner bottommost point C of the hollow in the pivot 7 of the load beam 5, at the moment the head body 1 is bonded to the bottom surface of the cantilever 6b of the flexure 6, there is a large tolerance occurring between the positions of the electrode terminal portion, formed at the trailing side Y end surface of the head body 1, and the connecting portion of the signal conducting pattern, so that the electrode terminal portion and the pattern connecting portion are out of line by a large amount, thereby preventing reliable positioning and bonding of both of these portions.
When the head body 1 is bonded to the bottom surface of the cantilever 6b of the flexure 6, with reference to the electrode terminal portion of the head body 1 and the signal conducting pattern connecting portion, no problems arise with regard to electrical contact between the head body 1 and the signal conducting pattern, but the bottommost point B of the pivot 7 of the load beam 5 and the predetermined location of the head body 1 are out of line by a greater amount.
The pivot 7 may be formed on the cantilever of the flexure 6. In this case, the tolerance produced in assembling the load beam 5 and the flexure does not add to any variations in the floating amount, so that when the head body 1 is positioned with reference to the connecting portion of the signal conducting pattern formed in the flexure 6, it is preferable that the pivot 7 be formed on the cantilever 6b.
However, as mentioned above, when the pivot 7 shown in FIG. 10 or FIG. 11A is formed by pressing, not only are the bottommost point B of the pivot 7 and the predetermined location of the head body 1 brought out of line by a large amount, but problems such as formation of a hole in the pivot 7 or distortion of the cantilever 6b may occur, since the film of the flexure 6 is very thin compared to the load beam 5.